Optical phased array device and the method therefor

ABSTRACT

An optical irregular phased-array is disclosed. The effective positions of the phase-controlled elements in the phased-array form an irregular array, such that the size of each phase-controlled element can be much larger than the wavelength of the light without having multiple beam problem. The effective phased-array is a virtual array of effective point-source of light, which is generated by an array of lenses or mirrors. An array of space-fed phase-modulators that is coupled with the array of lenses or mirrors provides means of adjusting the phase of the light from each effective point-source of light. While, the array of phase-modulators and array of lenses or mirrors can all be a regular array, which are simple in structure. A sub-array technique is provided to greatly reduce the controlling lines.

BACKGROUND OF THE INVENTION

The present invention relates to an optical phased-array thatelectronically steers a beam of light.

Phased-array is an array of plurality of phase-controlled element. Byadjusting the phase relationship among the electromagnetic waves (orother waves such that sonic wave) radiated from each phase-controlledelement, the electromagnetic waves radiated from each phase-controlledelement become in-phase in a given direction (or at a give position),thus, a constructive interference is formed, and therefore, thephase-array produces a high intensity beam in that direction. In otherdirections, the electromagnetic waves from each phase-controlled elementdo not meet the in-phase condition, and are cancelled out with eachother due to the interference, therefore, the radiation from thephased-array is close to zero. The geometric dimension of thephased-array (i.e. the aperture) determines the resolution of thephased-array (i.e. the width of the beam). The number of thephase-controlled element is related to the intensity of the beam. Thesignificant advantage of a phased-array device is that the phaserelationship among the electromagnetic waves radiated from eachphase-controlled element can be adjusted electronically, therefore, thebeam can be steered at extremely high speed.

For the prior art, to ensure that the phased-array radiates only onehigh intensity beam in the given direction, and that the radiation inother directions is close to zero, the distance between thephase-controlled elements (i.e. the center-to-center distance of theadjacent phase-controlled elements) must be less than half of thewavelength for which the phased-array is concerned (details will be inthe following).

It is well known that light is also an electromagnetic wave. In thefrequency range of light, the wavelength of the visible light is around0.4 to 0.7 micrometer, the wavelength of infrared is around 0.7 toseveral hundreds micrometer, and the wavelength of the ultraviolet isaround 0.4 to 0.04 micrometer. Now, let's use the 0.5 micrometerwavelength visible light as an example in the discussion of the prioroptical phased-array technology. As mentioned above, to ensure that thephased-array radiates only one high intensity beam in the givendirection while the intensity of the radiation is close to zero in otherdirections, the center-to-center distance between the phase-controlledelements has to be less than 0.25 micrometer. Thus, the size of thephase-controlled element itself must also be less than 0.25 micrometer.At present, the light source as the phase-controlled element, which isphase controllable, and is small enough in size does not exist yet.Therefore, the phased-array in optical frequency is to use a coherentbeam passing through many space-phase-modulators to create many beamswith particular phase relationship among them, i.e. each phase-modulatorproduces one beam with a given phase. Here, each phase-modulator is onephase-controlled element as mentioned above. Phase-modulator consists oftwo electrodes and electro-optical material between the two electrodes.The refractive index of the electro-optical material can be alerted in acertain rang according to the electrical field between the twoelectrodes, which alerts the optical path length as a beam of lighttravel trough the phase modulator, and therefore results phasemodulation (i.e. phase shifting). The electrical field between the twoelectrodes is controlled by adjusting the electrical potential on thetwo electrodes with a controller.

For the sack of the convenience, in this document, when the structure ofthe phased-array and phase-controlled element are concerned, width meansthe dimension in the direction perpendicular to the boresight of thephased-array (or simply called as dimension), the thickness means thedimension along the boresight of the phased-array.

Referring now to FIG. 1, a cross-section view of a prior art opticalphased-array device. It consists of a controller 11 and an array ofoptical phase-modulators 12 (it will be called as array ofphase-modulators in the following text for simplicity). The array ofphase-modulators consists of plurality of phase-modulators. Since theelectro-optical material 13 is the liquid-crystal, the phase-modulatorarray 12 possesses also a front window 14 and a rear window 15. Window14 and window 15 are usually flat plates, and parallel to each other.They are transparent in the optical frequency rang that they are workingwith. Each phase-modulator has a control electrode, denoted as 17 ₀, 17₁, . . . , 17 ₉, collectively referred as control electrodes 17.Phase-modulator consists of control electrode 17, common electrode 16and liquid-crystal 13. Common electrode 16 and control electrode 17 aretransparent in optical frequency range concerned. FIG. 1 illustrates thecross-section view of a one dimensional phase-modulator array. Controlelectrode 17 are plurality of parallel strip electrodes. The width ofthe strip electrode is denoted as w. The spacing between the electrodesis denoted as p. The center-to-center distance between adjacentelectrodes is denoted as d. d=p+w. The incident light 18 enters thephase-modulator array 12 from the rear window 15. Light isphase-modulated by each modulator, and the emitted light from eachmodulator becomes in-phase in direction θ, thus, a beam 19 is generatedin direction θ. The 46 represents the wavefront. The control lines 20,between the phase-modulator array 12 and controller 11 is for carryingthe control signal. The prior art requires that the center-to-centerdistance d to be less than the wavelength in order to ensure that thephased-array produces only one beam in the given direction. Otherwise,there will be other beams in other direction also, which is notdesirable. Therefore, prior art has to limit the width of thephase-modulator w (FIG. 1) to be less than the wavelength. Because ofthis, it produces the following problems:

1. For a give aperture of a phased-array, since the phase-modulator isvery small, the required number of the phase-modulator will be verylarge. For example, for the wavelength of 0.5 micrometer, 20,000 rows ofphase-modulator will be needed for each center meter aperture. Thismakes the structure of the phased-array device very complex, cost, anddifficult to fabricate.

2. The spacing p between the electrodes is limited by the insulationrequirement and fabrication process. For a given material andfabrication technology, the minimum p achievable can be regarded as aconstant. Obviously, the smaller the width of the phase-modulator w, thelarger the portion of the aperture that is occupied by the spacing, andtherefore, the lower the filling rate. For example, at wavelength of 0.5micrometer, assuming w and p are all 0.5 micrometer, then 50% of theaperture area is wasted, only half of the incident light is useful.

3. When the dimension of the phase-modulator (i.e. w. Same in thefollowing) is very small, the light entering the phase-modulatorsignificantly diverges due to diffraction, part of the light will enterneighboring phase modulators, which disturbs the light emitted from eachphase-modulator, and only a part of light emitted actually possesses thecorrect phase. Since the thickness of the phase-modulator is much largethan the width (e.g. the thickness is larger than 10 μm), the divergingof the light due to diffraction is very significant.

4. When the dimension of the phase-modulator is very small, the width ofthe electrode is also very small. Since the thickness of thephase-modulator is much larger than its width, i.e. the distance betweenthe electrodes are much larger than the width of the electrode itself,the infringing effect will significantly affect the uniformity of theelectrical field within the phase-modulator. Besides, since the distancebetween the electrodes is much larger than the width of the electrodes,the electrical field of neighboring phase-modulators also interfereswith each other significantly. Even if not taking count the disturb fromthe diverging light of neighboring phase-modulator, the effect due toinfringing electrical field would be significant enough to cause phaseerror in the light travel through each phase modulator.

The above four issues are the existing problems of the prior art. Thefirst and second problem are related to the fabrication cost and theperformance, while the third and forth problems are the fundamentalissues of the prior art. Because of these, so far, there is no practicaloptical phased-array device in the market.

Now, let's analyze the reason that the distance between phase-controlledelements has faced the limitation in the prior art. FIG. 2 illustrates aphased-array of eight phase-controlled elements, 21 ₀-21 ₇, collectivelyreferred as 21. The light with given phase emits from eachphase-controlled element. For simplicity, each phase-controlled elementis assumed to be a point source of light. If the light from each pointsource of light are all in-phase in the direction θ, therefore form aconstructive interference, it is said “the phased-array produces a beamof light in the θ direction”. In FIG. 2, that beam of light is denotedas 19 _(θ). The distance between adjacent point source of light isdenoted as d1, d2, . . . , d7. The optical retardation in the θdirection is denoted as δ1, δ2, . . . , δ7. From the geometricalrelationship, the followings are obtained:

δ1=d 1 sin θ  (1.1)

δ2=d 2 sin θ  (1.2)

δ7=d 7 sin θ  (1.3)

In order to make the light from each point source of light all in-phasein θ direction, it is necessary to adjust the phase of the light fromeach point source of light to compensate the optical retardationmentioned above. Therefore, the phase of the light from each pointsource of light must satisfy the following relationship:

The phase of 21 ₁ is ahead of 21 ₀ by δ1 (2π/λ),

The phase of 21 ₂ is ahead of 21 ₁ by δ2 (2π/λ),

 The phase of 21 ₇ is ahead of 21 ₇ by δ7 (2π/λ),

where, λ is the wavelength of the light. Taking into account theperiodicity of the wave, shifting the phase by an integer number of 2πdo not make any difference. For example, denoting δ1 (2π/λ)=k1(2π)+ω1,where k1 is an integer. Whether shifting the phase by k1(2π)+ω1 or byω1, the effect is the same. Therefore, in practice, the phase shiftingis always determined according to ω1 rather k1(2π)+ω1. In this document,when the phase shifting is mentioned, it always means that the 2π phaserest has been taken into account unless otherwise explicitly declared.

Now, let's consider the possibility that the light from eachphase-controlled element are also in-phase in other directions. Toanswer this question, let's analyze the array illustrated in FIG. 3.This array is same with the array in FIG. 2. Assuming the direction γwhich is different from direction θ, and denote optical retardation ofthe light from each phase-controlled element in the direction γ as α1,α2, . . . , α7. From the geometry relationship, we have:

α1=d 1 sin γ,  (2.1)

α2=d 2 sin γ,  (2.2)

α7=d 7 sin γ.  (2.3)

The phase difference of the light from each phase-controlled element indirection γ is denoted as φ1, φ2 , . . . , φ7. They contain two parts:One is the original phase difference among the point source of light(i.e. the phase shifting that has been implemented in order to achieveall the light in-phase in the direction θ); another is the phasedifference due to the optical retardation in direction γ. Therefore, thephase difference between adjacent phase-controlled elements in directionγ is as the following:

φ1=δ1 (2π/λ)−α1 (2π/λ),  (3.1)

φ2=δ2 (2π/λ)−α2 (2π/λ),  (3.2)

 φ7=δ7 (2π/λ)−α7 (2π/λ).  (3.3)

Or rewriting as:

φ1=d 1 (sin θ−sin γ)(2π/λ),  (4.1)

φ2=d 2 (sin θ−sin γ)(2π/λ),  (4.2)

φ7=d 7 (sin θ−sin γ)(2π/λ).  (4.3)

Here, same as before, φ1>0 means the phase of the light fromphase-controlled element 21 ₁ is ahead of 21 ₀ along the direction γ,otherwise, means the phase of the light from phase-controlled element 21₁ is behind of 21 ₀ along the direction γ. So on for the rest.

The above phase relationship can also be rewritten as:

φ2=φ1 d 2/d 1,  (5.1)

φ3=φ2 d 3/d 2,  (5.2)

φ7=φ6 d 7/d 6.  (5.3)

Only when φ1, φ2, . . . , φ7 are all equal to an integer (includingzero) number of 2π, the light from each phase-controlled element will beall in-phase in direction γ. In order to find out if it is possible tohave the light from each phase-controlled element to be all in-phase indirection γ, now let's introduce the unknown coefficients n1, n2, . . ., n7, and rewrite the above expressions in the following form:

φ1=n1 2π,  (6.1)

 φ2=n2 2π,  (6.2)

φ7=n7 2π.  (6.3)

The question that whether the light from each phase-controlled elementare all in-phase becomes the question that whether n1, n2, . . . , n7can all be integer.

From (5.1), (6.1) and (6.2), we have:

n2=n1d 2/d 1,  (7.1)

Similarly,

n3=n2d 3/d 2,  (7.2)

n7=n6d 7/d 6.  (7.3)

Assuming for a γ, n1 is equal to an integer, from (7.1) to (7.3), it canbe seen that unless d1, d2, . . . , d7 are equal to each other, or theyhave integer number of relationship with each other, n1, n2, . . . , n7can not all be integer. The prior art phased-array is the regular array,where the phase-controlled elements is equally spaced. d1, d2, . . . ,d7 are equal to each other:

d=d 1=d 2= . . . =d 7.  (8)

Therefore,

δ=δ1=δ2= . . . =δ7,  (9)

α=α1=α2= . . . =α7,  (10)

φ=φ1=φ2= . . . =φ7,  (11)

n=n1=n2= . . . =n7.  (12)

Thus, we can have equation:

sin θ=sin γ+nλ/d  (13)

Therefore, for a regular array, the question of whether the light fromeach phase-controlled element can all be in-phase becomes the questionof whether there is in integer n to satisfy the above equation.

In the following, the discussion will be for the case of 0≦θ<π/2 (forthe case of −π/2<θ<0, the analysis is similar). In FIG. 2 and FIG. 3, ifθ>0 corresponds to deflecting light up, then θ<0 corresponds todeflecting light down, and θ=0 means light beam points the boresight ofthe phased-array.

When 0≦θ<π/2, then 0≦sin θ<1, thus,

0<sin γ+nλ/d<1.

Rewriting it as the following, and call it the “main condition”:

−nλ/d≦sin γ<1−nλ/d  (14)

As mentioned above, whether the light from each phase-controlled elementcan all be in-phase in direction γ can be determined by if n can be aninteger. In the following, we analyze the possibility that n is aninteger. For n=0, γ=θ. This is not consistent with the assumption that“the direction γ is different from direction θ. Therefore, the case ofn=0 will not be considered. In the following, for d=2λ, d=λ, d=λ/2 threecases, we will discuss n±1, n±2, . . . , respectively.

Substituting d=2λ into (14):

−n/2≦sin γ<1−n/2  (15)

Substituting all possible n values that can satisfy the above equation:

For n=1, (1.5) becomes:

−0.5≦sin γ<0.5  (16)

From this, we know that the γ that satisfies (16) is within the range of−π/6˜π/6. For γ within this range, the sin θ is in range of 0˜1.Therefore, when output beam from the phased-array is within the range of0˜π/2, there is a accompanying beam in the range of −π/6˜π/6.

For n=−1, (15) becomes:

0.5≦sin γ<1.5  (17)

The γ that can satisfy this condition is in range of π/6˜π/2. Thecorresponding θ is in the range of 0˜π/6.

For n=2, (15) becomes:

−1≦sin γ<0  (18)

The γ that can satisfy this condition is in range of −π/2˜0. Thecorresponding θ is in the range of 0˜π/2.

For n=−2, (15) becomes:

1≦sin γ<2  (19)

This condition can be satisfied only when γ=π/2, correspondingly, θ=0.

For n=3, (15) becomes:

−1.5≦sin γ<−0.5  (20)

The γ that can satisfy this condition is in range of −π/2˜−π/6. Thecorresponding θ is in the range of π/6˜π/2.

Other integer n can not satisfy (14). The results are summarize infollowing:

n=1, the range of γ: −π/6˜π/6, the range of θ: 0˜π/2.

n=−1, the range of γ: π/6˜π/2, the range of θ: 0˜π/6.

n=2, the range of γ: −π/2˜0, the range of θ: 0˜π/2.

n=3, the range of γ: −π/2˜−π/6, the range of θ: π/6˜π/2.

Therefore, when θ is in the range of 0˜π/6, there are three accompanyingbeams. When θ is in the range of π/6˜π/2, there are also threeaccompanying beams. When θ=0, there are two accompanying beams. Whenθ=π/6, there are also two accompanying beams. (In the above, the casesof γ=π/2 or −π/2 are not taken into account. The same will be for thefollowings).

Substituting d=λ into (14):

 −n≦sin λ<1−n  (21)

Substituting all possible n values into the condition as in the case ofd=2λ. The results are: Only when n=1, there is an accompanying beam. Therange of the γ is −π/2˜0; the range of θ is 0˜π/2. When θ=0, thecorresponding γ is π/2 and −π/2, and there is just no accompanying beam.

Substituting d=λ/2 into (14):

−2n≦sin γ<1−2n  (22)

No matter what integer value of the n is, there is no γ that can satisfythis condition. Therefore, there is no accompanying beam, no matter whatrange the θ is. However, when θ=π/2, we have n=1, and correspondingly,γ=−π/2. The accompanying beam is just about to occur, but just have notoccurred yet. It can be deduced tllat when d>λ/2, there will beaccompanying beam.

In above, we have calculated d=2λ, λ, λ/2 three cases. The rule for theoccurrence of the accompanying beams is that: the larger the d, the morethe accompanying beams; when d is less than λ/2, there is noaccompanying beam.

In practical application, the scanning angular range is often muchsmaller than π/2. At that time, the maximum d can be larger than λ/2without introducing an accompanying beam. For example:

From (13), take n=1, γ=−π/2 (i.e. the accompanying beam is about tooccur but have not occurred yet), for difference scanning angular range,the maximum d is determined as followings:

When θ=−30°˜30°, d=0.67λ,

When θ=−10°˜10°, d=0.85λ,

When θ=−5°˜5°, d=0.92λ.

When θ=−1°˜1°, d=0.98λ.

The above analysis has explained why prior arts require to place thephase-controlled elements in a spacing less than half wavelength or lessthan one wavelength. If the distance between phase-controlled element isless than the wavelength, then, the dimension of the phased-controlledelement itself must be smaller than the wavelength.

In practical application, the maximum d without accompanying beam can beeven larger. For example, if limiting the light from eachphase-controlled element in the angular range corresponding to theangular range of the scanning of the beam from the phased-array, then,beyond this angular range, even if the condition for accompanying issatisfied, there will still be no accompanying beam. The maximum d canbe estimated as following:

From (13), take n=1, γ=−θ(i.e. the accompanying beam is about to occurbut has not occurred yet), for different scanning angular range, themaximum d can be determined. Some examples are listed below:

When θ=−30°˜30°, d=λ,

When θ=−10°˜10°, d=2.8λ,

When θ=−5°˜5°, d=5.7λ,

When θ=−1°˜1°, d=28λ.

In summary, for prior art, there is always a restriction in the distancebetween the phase-controlled elements by the wavelength. When thedistance between the phase-controlled elements is larger than thewavelength, the scanning angular range decreases rapidly as the distanceis enlarged.

U.S. Pat. No. 5,093,740 (issued on Mar. 3, 1992) by Dorschner etc.described a liquid-crystal based array of longitudinal phase-modulators,as shown in FIG. 1. This patent also described a sub-array method toreduce the control lines. But this patented technology limited thescanning angle to some special, discrete values. Furthermore, even ifthe sub-array method is used, its number of control line is still alarge number. Therefore, that device does not have much significance inpractical application.

Before describing the principle and method of the present invention,let's briefly describe the sub-array method of prior art. Referring nowto FIG. 1. The strip electrodes are grouped, and each group becomes asub-array. Each sub-array has plurality of phase-modulators. For eachphase-modulator at the corresponding position in each sub-array, itscontrol electrode is connected in parallel, and is controlled inparallel by the controller. FIG. 4 describes the phase relationshipamong the phase-controlled elements in each sub-array and among thesub-arrays. The figure illustrates three adjacent sub-arrays: 30 ₁, 30 ₂and 30 ₃. In FIG. 4, the horizontal axis represents the geometricposition of each phase-modulator, and the stair-like line represents thephase of each phase-modulator. Since in each sub-array, thephase-modulator of the corresponding position is controlled in parallel,the shape of the stair-like line 22 is identical for the threesub-arrays. That is to say that within each sub-array, the light in thegiven direction is all in-phase. However, the light among the sub-arraysis not necessary to be in-phase in the given direction. The mis-match ofthe phase among sub-arrays can be illustrated with phase relationship atthe boundary between two adjacent sub-arrays, as shown in FIG. 4. InFIG. 4, on the boundary I_(1,2) of two adjacent sub-arrays 30 ₁ and 30₂, the stair-like line 22 have a phase difference β. In general, β isnot equal to zero or 2π. On the boundary I_(2,3), the situation issimilar. Therefore, for the prior art, only when the beam of the lightis in some special directions such that the β is happen to be equal tozero or 2π, the light from each sub-array will become in-phase with eachother. In all other directions, β is not equal to zero or 2π, the phaseof the light from each sub-array does not match with each other, and thephased-array can not work. Therefore, the sub-array technique proposedby Dorschner etc. can only deflect beam to some special discrete angles.This obviously affects its practical applications.

James A. Thomas, Mark Lasher etc. used the cascade of two scanner tosolve the problem of phase mis-match among sub-array, referring to“Optical Scanning Systems: Design and Applications”, Leo Beiser andStephen F. Sagan, Ed., Proc. SPIE 31, pp.124-132(1997). However, theystill did not overcome the problems caused by the limitation ofwavelength on the size of phase-controlled element and on the spacingbetween the phase-controlled elements. These problems include: Scanningangular range is extremely small, and number of scanning lines is lessthan the number of rows of the phase-controlled elements.

SUMMARY OF THE INVENTION

The present invention provides an optical phased-array device. The saiddevice consists of plurality of phase-controlled elements that form anirregular phased-array, and means to control the phase relationshipamong the light from each phase-controlled element such that to deflecta beam of light in a given direction; the effective position of thephase-controlled elements form an irregular pattern, and the averagedistance between the adjacent phase-controlled elements is substantiallylarger than the wavelength of the light.

An optical phased-array device according to the present invention,wherein irregular phased-array consists of plurality of sub-arrays whichconsists of plurality of phase-controlled elements; the effectivepositions of the phase-controlled elements of the sub-array formirregular pattern, and the effective array of the sub-arrays are alsoirregularly arranged with respective to each other.

The present invention also provides method to control sub-arrays, whichincludes parallel controlling of the sub-arrays and independentcontrolling of each sub-array. Sub-array controlling method alsoincludes additional phase-modulator for sub-array phase compensation.

An optical phased-array device according to the present invention alsoincludes the array of lenses or mirrors, which are coupled with thephase-modulators; whereby, forming virtual array of point source oflight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the cross-section view of a prior art regular phased-arraydevice.

FIG. 2 is the schematic for illustrating the principle that phased-arraytechnology generates a beam in θ direction.

FIG. 3 is for the explanation of multiple beam phenomenon in thephased-array technology.

FIG. 4 illustrates the phase mismatch among the sub-arrays of the priorart sub-array technique.

FIG. 5 is the cross-section view of some phase-controlled elements ofone type of embodiment of the irregular phased-array.

FIG. 6 illustrates the array of longitudinal phase-modulators based on-solid electro-optical material.

FIG. 7 illustrates the array of transverse phase-modulators based onsolid electro-optical material.

FIG. 8 illustrates a single phase-modulator and the corresponding lensfor the irregular phased-array.

FIG. 9 is another arrangement for the lens.

FIG. 10 is a two-dimensional phased-array formed by two one-dimensionalarrays of phase-modulators and a two dimensional array of lenses.

FIG. 11 illustrates how to construct a two-dimensional array ofphase-modulators with two groups of electrodes.

FIG. 12 is a two-dimensional array of transverse phase-modulators,wherein each modulator can be independently controlled.

FIG. 13 is a two-dimensional array of longitudinal phase-modulators,wherein each modulator can be independently controlled.

FIG. 14 is another type of two-dimensional array of longitudinalphase-modulators, wherein each modulator can be independentlycontrolled.

FIG. 15 illustrates the connection of the control lines for thesub-arrays of the irregular phased-array.

FIG. 16 illustrates the phase match among sub-arrays.

FIG. 17 illustrates the phase match among sub-arrays in the irregularphased-array.

FIG. 18 illustrates the sub-array technique using additional sub-arrayphase compensation phase-modulators.

FIG. 19 illustrates the structure of a two-dimensional phased-arrayhaving sub-arrays with additional phase compensation phase-modulators.

FIG. 20 illustrates the structure of a one-dimensional phased-arrayhaving sub-arrays with additional phase compensation phase-modulators.

FIG. 21 illustrates how to construct the sub-array phase compensationphase-modulator with transverse phase-modulators.

FIG. 22 illustrates the irregular placement of the sub-arrays.

FIG. 23 illustrates another irregular placement of the sub-arrays.

FIG. 24 illustrates the two-dimensional irregular placement of thesub-arrays.

FIG. 25 illustrates the array of phase-modulators for the sub-arrayphase compensation in a two-dimensional phased-array.

FIG. 26 illustrates the reflective phased-array device.

FIG. 27 illustrates the principle of the reflective phased-array.

FIG. 28 illustrates the principle of the tilted mirror in the reflectivephased-array.

FIG. 29 illustrates the phased-array constructed with small sizephase-controlled light emitters.

FIG. 30 illustrates the phased-array constructed with large sizephase-controlled light emitters and lenses.

FIG. 31 illustrates the phased-array constructed with large sizephase-controlled light emitters, phase-modulators and lenses.

DETAILED DESCRIPITION OF THE INVENTION

1. The Principle of the Irregular Phased-array

For the prior art optical phased-array, the phase-controlled elementsform a regular pattern, i.e. d1=d2= . . . =d7 (referring to FIG. 2),while, for the present invention, the phase-controlled elements form anirregular pattern. Generally, the distances between the adjacentphase-controlled elements are not equal to each other, and there is alsono integer relationship or other special relationship among them.Therefore, in the expression (7.1) to (7.3), n1, n2, . . . , n7 can notall be integer at same time. That is to say: no matter what ratio of d/λis, there is always no accompanying beam. In an irregular phased-array,the rule of the placing the phase-controlled element can be stated as:The distance between the phase-controlled elements is a random variable,which follows a certain distribution within a certain range, forexample, a uniformly distributed random variable within a certain range.For example, the distance between phase-controlled elements assumes avalue within 0-2d with equal probability. Thus, the average distancebetween the phase-controlled elements will be the d. When there isenough number of the phase-controlled elements (e.g. over thousand), theintensity of the radiation from the phased-array in the directions otherthan the beam is negligibly small in relative to the intensity of thebeam. In the following, the principle of the irregular phased-array willbe further explained with some examples of the embodiment.

Because the phased-array of the present invention is an irregular array,there is no accompanying beam problem when the d is larger than thewavelength of the light. In designing the irregular phased-array, thewidth of the phase-modulator or the center-to-center distance of twoadjacent phase-modulators can assume a much larger value than thewavelength of the light; it can be tens of times to thousands of timesof the wavelength, or even larger. This is a significant advantage ofthe irregular phased-array.

2. Array of Lenses and Virtual Array of Effective Point-source of Light

FIG. 5 is a part of the cross-section view of an embodiment of theirregular phased-array. This device includes controller 11 andphase-modulator array 12, and array of lenses 23 ₀, 23 ₁, . . . ,collectively referred as 23. The array of lenses is a distinguishfeature of the present invention. The 27 ₀, 27 ₁, . . . are the focalpoints of the lenses, collectively referred as 27. The d1, d2, . . . ,are the distance between the focal points of the adjacent lenses. Thephase modulator consists of mainly the control electrode 17, the commonelectrode 16 and the electro-optical material 13 between the twoelectrodes. Plurality of phase-modulator form an array ofphase-modulator 12. In the irregular phased-array, the phase-modulatorand the lens 23 coupled with the phase-modulator form a phase-controlledelement. Plurality of the phase-controlled elements form an irregularphased-array. Or in other words, it can be regarded that the irregularphased-array is formed with an array of phase-modulators and an array oflenses. The phased-array, controller and control lines form aphased-array device. Controller 11 controls the phase of the light fromeach phase-controlled element to make light from each phase-controlledelement all in-phase in a given direction. Thus, the phased-arrayproduces a beam of light 19 in the given direction, e.g. the θ. Thisbeam can also be focused with a lens to a surface (e.g. a screen).

In FIG. 5, the 46 represents the wave front, the 18 is the incidentlight. Light shielding strip 24 is the collection of the individuallight shielding strip 24 ₁˜24 ₉. The light shielding strip isnon-transparent, and is used to lock the light from entering the space25 between the phase-modulators. The difference between the FIG. 5 andFIG. 1, besides the array of lenses, is also on that in the FIG. 5, thecommon electrode 16 forms plurality of mutually independent electrodesaccording to the division of the sub-arrays. Each sub-array has a commonelectrode 9 that is independent of other sub-arrays (details in the textbellow). Furthermore, in FIG. 5, the width w of the control electrode 17is much larger than the wavelength of the light, for example, it can betens of times to thousands of times of the wave length of the light, oreven larger. Such large width is impossible for the prior arts.

The common electrode 16 and the control electrode 17 in the FIG. 5 canexchange their position, i.e. placing the 16 at the side of light outputand placing 17 at the side of light incident, the results is the same.

In FIG. 5, ten phase-controlled elements are illustrated. In practicalapplication, the irregular phased-array usually contains large number(e.g. over a thousand) of phase-controlled element. The phase-modulatorcan also be constructed with a wave duct (e.g. optical fiber). At thistime, the phase-modulator consists of a wave duct of certain length,which is made of electro-optical material and has electrodes on it.

In the irregular phased-array, besides the liquid-crystal, there aremany other electro-optical material that can be used, including: LiNbO₃,TiTaO₃, BBO, KDB, KDP, BSO, BGO, KTP, KNbO₃, LiIO₃, ZnSe, and polymers.There are many this type of material, and we are not going to mentionall of them here.

What FIG. 5 illustrated is only one particular embodiment of the presentinvention. The present invention is not limited to be that particularembodiment. Furthermore, the lens that forms the array of lenses can beconvex lens, concave lens or diffractive lens etc. In the case of convexlens, the light is focused to the focal point, and then diverges fromthe focal point. In the case of concave lens, the light diverges as iffrom the virtual focal point. The lens can also be a cylindrical lensfor one-dimensional scanning application. Similar to the focal point ofa spherical lens, the cylindrical lens has focal line (for thesimplicity, it will still be called as focal point). By choosing theoptical parameter of the lens such as aperture, focal length, a properdivergent angle of the light can be obtained. The diverge angle shouldmatch with the deflection angular range of the phased-array. If thedivergent angle is too small, it will not satisfy the need in the entiredeflection angular range. If the divergent angle is too large, it willwaste the light, and lower the efficiency of the system.

In this writing, it is assumed that the incident beam of light isparallel to the optical axes of the lens when the action of the lens isdescribed, unless otherwise stated. If the incident beam of light is notparallel to the optical axes of the lens, the beam will be focused tosome where on the focal plane instead of on the focal point. But, thereis no essential difference for what we are concerned here.

A lens is coupled with a phase-modulator, to focus the light from thephase-modulator (using convex lens as example. Same for the rest of thetext), and then diverges the light from the focal point with a certaindivergent angle. Here, one phase-controlled element includes onephase-modulator and one lens coupled with the phase-modulator.

The location of the periphery of the lens corresponds to the location ofthe periphery of the phase-modulator. The center determined based on theperiphery of the lens is called the geometric center of the lens. Thecenter determined based on the periphery of the phase-modulator iscalled the geometric center of the phase-modulator. The geometric centerof the phase-modulator usually coincides with the geometric center ofthe lens, and usually collectively referred as geometric center of thephase-controlled element. The center-to-center distance between adjacentphase-modulators is the distance between the geometric centers of theadjacent phase-modulators, and is simply called as distance between thephase-controlled elements.

After having adapted the lens, the light from each phase-controlledelement of the phased-array appears to be emitted as if from apoint-source at the focal point of the lens, furthermore, it is aphase-controllable point-source of light. Of course, it is not a realpoint-source of light, therefore, is called effective point-source oflight.

As viewed from the boresight of the phased-array, the optical axes (andthe focal point on the optical axes) usually does not coincided with thegeometric center of the lens (and the geometric center of thephase-modulator). When determining the phase relationship among thelight from each phase-controlled element, what is concerned is theposition of the focal point of the lens, while the geometric position ofthe lens is no longer directly relevant any more. Therefore, theposition of the focal point of the lens is defined to be the effectiveposition of the phase-controlled element. Correspondingly, the irregulardistance between the phase-controlled elements in the irregularphased-array is the distance between the effective positions of thephase-controlled elements.

Thus, in fact, it produces an virtual array wherein the effectiveposition of the phase-controlled element follows an irregular pattern.In other words, the virtual array is the array of the effective positionof the phase-controlled element. It is called virtual array of effectivepoint-source of light, after the light source has been included. Theabove method of defining the effective position of the phase-controlledelement and producing the virtual array of the effective point source oflight can be used for both irregular phased-array and regularphased-array.

Using the lens and introducing the concepts of effective position of thephase-controlled element and virtual array of effective point-source oflight make the design and fabrication of the optical phased-array deviceeasier, and make a practically useful optical phased-array possible.

It needs to be pointed out that such phased-array based on virtual arrayof effective point source of light can also be realized with mirrors(detailed description later).

FIG. 6 and FIG. 7 illustrate the array of one-dimensionalphase-modulators that are constructed with solid electro-opticalmaterial 13. Though the solid electro-optical material usually has weakelectro-optical effect than that of liquid-crystal, the response speedis much faster. Thus, when the beam changes its direction of thedeflection, the switching speed can be as high as 10 ⁻¹² second. Due tothe usage of the solid electro-optical material, in FIG. 6 and FIG. 7,there are no front window 14 and rear window 15 of FIG. 5. This isbecause that the solid electro-optical material can maintain its ownshape. As shown in FIG. 6, in the phase-modulator, the electric fielddirection Z is parallel to the direction of light propagation 19,therefore, this is a longitudinal phase-modulator. The transparentcontrol electrode 17 and common electrode 16 are directly attached tothe electro-optical material 13. In the transverse phase-modulator, asshown in FIG. 7, the electric field direction y is perpendicular to thedirection of light propagation 19; the phase-modulator is consists ofelectro-optical material 13 and the electrodes 17 and 16 on the two sideof the electro-optical material respectively. The phase-modulators arestacked together with insulator layer 26 between them. The structureshown in FIG. 6 and FIG. 7 coupled with the array of lenses can be usedto construct the irregular phased-array.

FIG. 8 is an example of a phase-modulator with the lens 23 for thephased-array. The lens has a focal point 27. It can be seen from theFIG. 8 that the focal point is on the optical axis but is not necessaryon the geometric center 29 of the lens or the phase-modulator. Thedifference between the geometric center and the optical axes can be seenfrom the FIG. 8. Just as purposely illustrated in FIG. 8, the lens canbe, and usually is, asymmetrical. The focal point 27 of the lens is theeffective position of the phase-controlled element of the irregularphased-array. The major feature of the irregular phased-array is thatthe effective positions of the phase-controlled element form anirregular pattern. The lens can also be placed at other side of thephase-modulator, as shown in FIG. 9.

3. Two-dimensional Irregular Phased-array

What is illustrated in FIG. 5 is a one-dimensional phased-array, whichconsists of a one-dimensional array of phase-modulators and aone-dimensional array of lenses. The lens can be a cylindrical lens, andthe focal line of each cylindrical lens is usually on the same plane. Aone-dimensional phased-array can deflect beam of light along onedirection, i.e. it can do line scanning. If we need to scan the beam oflight along two directions, i.e. scanning over a surface, we need atwo-dimensional phased-array. For a two-dimensional phased-array, boththe array of phase-modulators and the array of lenses aretwo-dimensional array.

In the following, we will describe several examples of the structure oftwo-dimensional array of phase-modulators.

FIG. 10 illustrates two one-dimensional arrays 12 of longitudinalphase-modulators. The strip electrodes of the two arrays ofphase-modulators are perpendicular to each other. The twoone-dimensional arrays are cross cascaded to form a two-dimensionalarray of phase-modulators, then, they are coupled with a two-dimensionalarray of lenses 23 to eventually form a two-dimensional phased-array.Where each phase-modulator in the two-dimensional array of thephase-modulators is formed by the superimposed portion of twoone-dimensional (stripe) phase-modulators in the direction of lightpropagation. One of the two one-dimensional arrays of phase-modulatorsdeflects the beam of light in the first dimension, and the anotherone-dimensional array of phase-modulators deflects the beam of light inthe second dimension. The two groups of control signal for controllingthe beam to deflect in the two directions are applied to the twoone-dimensional arrays of phase-modulators respectively. Of course,similarly, we can also use two one-dimensional arrays of transversephase-modulators to construct the two-dimensional array ofphase-modulators. When the one-dimensional array of phase-modulatorscontains sub-array, the two-dimensional array of phase-modulators formedin this way will naturally contain two-dimensional sub-arrays (detailsin the following text).

FIG. 11 illustrates another way to construct a two-dimensional array ofphase-modulators. Two groups of strip electrodes 17 that areperpendicular to each other are placed to the two sides of theelectro-optical material 13 to form a two-dimensional array ofphase-modulators. Each phase-modulator in this two-dimensional array ofphase-modulators is formed by the two strip electrodes and theelectro-optical material between the two electrodes. With atwo-dimensional array of lenses, a two-dimensional phased-array isconstructed. The two groups of control lines connect to the two groupsof electrodes respectively to control the beam of light to havetwo-dimensional deflection. The two-dimensional array ofphase-modulators in FIG. 11 is essentially same with the two-dimensionalarray of phase-modulators in FIG. 10, but the structure of thetwo-dimensional array phase-modulators in FIG. 11 is more compact. ForFIG. 11 and FIG. 10, the characteristics of the control signals that aresend to the two groups of electrodes are the same, except that thepolarity of the two groups of signals are opposite to each other in FIG.11. Of course, a non-zero electric potential can also be used asreference potential for these two groups of control signals.

Obviously, each phase-modulator in the two-dimensional array ofphase-modulators shown in FIG. 10 or FIG. 11 is not controlledcompletely independent, since the controller sends control signal to thetwo groups of the strip electrodes rather than to each individualphase-modulator independently. The advantage of the structure shown inFIG. 10 and FIG. 11 is that the control signals for the two directions(two dimensions) are independent with each other, thus, the number ofcontrol lines are significantly reduced. Since each of the two groups ofthe control signal for the two-dimensional array of phase-modulatorsneeds a maximum phase shift of one wavelength (2π), the maximum phaseshift needed for each phase-modulator in the two-dimensional array ofphase-modulators corresponds to two wavelength, i.e. 4π.

Another scheme of the two-dimensional array of phase-modulator isdifferent from the scheme of strip electrodes as shown in FIG. 10 orFIG. 11, it sends signal to each phase-modulator separately, and makesindependent control of each phase-modulator. If using this scheme, eachphase-modulator needs maximum phase shift 2π only, and the beam of lightcan be focused in three-dimensional space.

FIGS. 12, 13, and 14 illustrate the two-dimensional array ofphase-modulators in which each phase-modulator can be independentlycontrolled, then, coupled with the array of lenses, a two-dimensionalphased-array is constructed.

FIG. 12 illustrates a two-dimensional array of phase-modulators withtransverse phase-modulator. The incident light 18 comes in X direction,the control electric field applied to the phase-modulator is in Zdirection, perpendicular to incident beam. The control electric field isproduced by the electric potential difference on the control electrode17 and common electrode 16. Each phase-modulator can be independentlycontrolled. An irregular phased-array based on that can focus the beamin three-dimensional space. The array of phase-modulators of such devicehas several layers. There is insulator layer 26 between the layers ofphase-modulators to isolate the electrodes of the phase-modulators ofeach layer. The electro-optical material 13 used in such array is thesolid electro-optical material.

FIG. 13 illustrates a two-dimensional array of phase-modulators withlongitudinal phase modulation. Each phase-modulator can be independentlycontrolled. The incident light 18 enters the phase-modulator along Xdirection, and the electric field of the control signal in thephase-modulator is also along the X direction in parallel with theincident light. In this structure, the common electrode 16, controlelectrode 17 and the control line 20 connects to each electrode are alltransparent. There is the transparent insulator layer between thecontrol line 20 and control electrode 17, which makes the control lineconnects to the control electrode 17 of a individual phase-modulator.

FIG. 14 is another type of two-dimensional array of longitudinalphase-modulators. Sixteen phase-modulators are shown in the figure. Thestructures of FIG. 14 and FIG. 13 are similar. The only difference isthat in the FIG. 14, the control line 20 is placed in the gap betweenthe phase-modulators.

4. The Placement of the Phase-controlled Element in the IrregularPhased-array

For the phase-controlled element described above, the focal point of thelens is the effective position of the phase-controlled element, and thearray of the focal points 27 of the lenses, as shown in FIG. 5, is thearray of the effective positions. By shifting the position of the focalpoint, the irregular placement of the effective position of thephase-controlled element can be obtained. Therefore, it can be done inthis way: the geometric position of the phase-controlled element itselfforms a regular array while the effective position of thephase-controlled element forms an irregular array. In other words,though we have constructed an irregular virtual array of effectivepoint-source of light, the array of phase-modulators can still be aregular array. The geometric position of the lens can also be a regulararray. It only needs to shift the optical axis 28 of the lens 23 (FIG. 8and FIG. 9) to alert the position of the focal point such that the focalpoints form an irregular array. Since the geometric position of thephase-controlled element is placed in a regular pattern, this methodsimplifies the fabrication of the phase-modulator array 12, and enhancesthe overall efficiency of the irregular phased-array device.

If the variation range of the effective position of a phase-controlledelement is from 0 to d, the variation range of the effective distance(i.e. distance between the effective positions) between two adjacentphase-modulators will be 0 to 2d. Such large variation on the effectivedistance between adjacent phase-controlled elements is indeed theadvantage of employing the array of lenses in the irregularphased-array. In fact, the optical axis of the lens does not have to bewithin the boundary of the phase-modulator. The structure of the opticallens can even shift the optical axis to outside of the periphery of thelens.

The another way to make the phase-modulator form irregular pattern is touse phase-modulator of irregular size. In this way, though it can alsokeep the spacing between the phase-modulator constant, the structure ofthe array of phase-modulator and the array of lenses become verycomplex.

When the size of the phase-controlled element is comparable to thewavelength, the geometric center of the phase-controlled element is theeffective position of the phase-controlled element. When distancebetween the phase-controlled elements is much large than the wavelength,it is possible to let the phase-controlled element itself to form anirregular pattern to realize the irregular phased-array.

As mentioned before, the distance between the effective positions of theadjacent phase-controlled elements is a random variable within a certainrange, its value can be generated by the random number generator of acomputer. For a given condition, there can be many in principleequivalent arrangement of the effective positions of thephase-controlled elements. A good arrangement should make the backgroundradiation of the phased-array low and uniform. The best arrangement canbe selected from various arrangements through computer simulation.

It is relatively simple to have a one-dimensional array ofphase-controlled elements to form an irregular pattern: The distancebetween the effective position of the adjacent phase-controlled elementsis a random variable within a certain range.

To form an irregular pattern for a two-dimensional array ofphase-controlled elements, there are two ways. One method is to placethe effective position of phase-controlled elements in columns and rows,and the distance between the columns and rows is a random variablewithin a certain range. This method is particularly suitable to thetwo-dimensional phased-array as shown in FIG. 10 and FIG. 11. Anothermethod is to place the effective position of the phase-controlledelements in a completely random pattern (i.e. they are no longer alignedin columns and rows). This method is suitable to the two-dimensionalphased-array as shown in FIG. 12, FIG. 13 and FIG. 14.

No matter how the effective position of the phase-controlled elementforms an irregular pattern, for a particular irregular phased-array, theeffective position of each phase-controlled element is known, and thephase-relationship among the phase-controlled elements and the phaseshift needed are all determined based on the effective position of eachphase-controlled element.

5. Sub-array Control

The present invention further proposed the sub-array technique for theirregular phased-array, to further simplify the irregular phased-arraydevice and controller, and to reduce the control lines between thephased-array and the controller. The method is to divide thephased-array into plurality of sub-arrays. Each sub-array is identical.Here, the identical means that in each sub-array, the effective positionof the phase-controlled element is placed in a same pattern, but in eachsub-array, the placement of the geometric position, shape, size of thephase-controlled elements can be either identical or not identical, eventhe number of phase-controlled elements can be identical or notidentical. The controller controls each sub-array in parallel, i.e. thecorresponding phase-controlled elements in each sub-array receives thesame control signal from the controller. Therefore, the controlelectrode of the corresponding phase-controlled element in eachsub-array are connected in parallel.

FIG. 15 illustrates connection of the electrodes of an irregularphased-array with sub-arrays for the structure shown in FIG. 5. InFIG.15, the control electrodes 17 _(1,1,) 17 _(2,1), . . . , 17 _(m,1)of sub-array 30 ₁, 30 ₂, . . . , 30 _(m) are all connected in parallelto the control line 17 ₍₁₎, and receive the same control signal. But ineach sub-arrays, the phase-controlled element on different position hasits own control line 17 ₍₁₎, 17 ₍₂₎, . . . ., 17 _((n)). The controller,through the each control line, makes independent control on the eachgroup of phase-controlled elements that are on different positions ineach sub-array.

For the present invention, each sub-array has its own common electrode.In FIG. 15, 16 ₁, 16 ₂, . . . , 16 _(m) are the common electrodes ofsub-array 30 ₁, 30 ₂, . . . , 30 _(m) respectively. The controller canindependently control the common electrode of each sub-array. This isvery different from the sub-array technique of prior arts.

In each sub-array, if taking the zero volt electric potential as thereference electric potential, the electric potential applied to thecontrol electrode of each phase-modulator varies from zero to a positivevalue, while the electric potential applied to the common electrode ofeach phase-modulator varies from zero to a negative value. The controlsignal applied to each control electrode makes the phase-modulators thatare at the same corresponding position in each sub-array generate a sameamount of phase-modulation. While the control signal applied to thecommon electrode of each sub-array generate an additional amount ofphase-modulation for the entire sub-array, in order to have the phase ofthe light from each sub-array match with each other. It should bepointed out that exchanging the polarity between the control electrodeand common electrode or using other non-zero electric potential as thereference, the result will be essentially the same.

Therefore, the present invention has both capabilities of controllingeach sub-array in parallel and controlling each sub-array independently.FIG. 16 is used to illustrate the sub-array controlling method of thepresent invention. In the figure, the horizontal axis represents theposition of the phase-modulator and sub-array, and the vertical axisrepresents the phase relationship of each phase-controlled element andthree sub-arrays 30 ₁, 30 ₂, and 30 ₃. In the given direction, the lightfrom each phase-controlled element within a sub-array is in-phase witheach other, however, the light from different sub-arrays is generallynot in-phase with each other in the given direction. In the presentinvention, the common electrode of each sub-array is independentlycontrolled, therefore, it is possible to independently alert theelectric potentials on the common electrode 16 ₁, 16 ₂, . . . , 16 _(m)(FIG. 15) of each sub-array, to make the stair curve 22 shift up or down(FIG. 16) until phase match among the light from each sub-arrays isachieved. As shown in FIG. 16, with the method of present invention, itis always possible to adjust the phase difference between two adjacentphase-controlled elements belonging to two adjacent sub-arrays to β=0 orβ=2π (FIG. 4). It can be seen in FIG. 16 that the shape of the staircurve 22 of the sub-array 30 ₂ is same (with others), but curve has beeshifted upward. In the figure, at I_(1,2) and I_(2,3), the stair curvesmatch with each other. The range of the phase-modulation needed for eachphase-modulator increases one more wavelength, i.e. 2π.

In irregular phased-array, the phase-controlled elements form anirregular pattern. FIG. 17 illustrates the application of the sub-arraycontrolling method of the present invention in the case of irregularphased-array. In the figure, the horizontal axis represents theeffective position of the phase-controlled element, and the verticalaxis represents the phase relationship among the phase-controlledelements of three adjacent sub-arrays 30 ₁, 30 ₂, and 30 ₃. In thefigure, the irregular phased-array is presented as the irregularitiesamong the length and height of each step of the stair curve. However,besides the length of the last step, the shape of the stair curve 22 ofeach sub-array is identical. The difference of the length of the laststep is to illustrate the irregular placement of the irregularsub-arrays in the phased-array (details will be in the following). Thefigure also illustrates the match of the wavefront of each sub-array.The sub-array controlling method of the present invention can be usedfor regular phased-array as well as for irregular phased-array.

The method mentioned above that realizes the phase-match among thesub-arrays in a given direction through the controlling of the commonelectrode of each sub-array can be used for one dimensional phased-arraysuch as shown in FIG. 5, FIG. 6 and FIG. 7, and for two-dimensionalphased-array as shown in FIG. 10. For the two-dimensional phased-arrayas shown in FIG. 11, an additional sub-array phase compensationphase-modulator 31 is needed for each sub-array to shift the stair curveas shown in FIG. 16 in order to realize the phase match among thesub-arrays, as illustrated in FIG. 18. The structure of the sub-arrayphase compensation phase-modulator is same with the two-dimensionalarray of phase-modulator shown in FIG. 11, but the width of its stripelectrode is the size of the sub-array. The control method for thesub-array phase compensation phase-modulator is also similar with thatfor the two-dimensional array of phase-modulators shown in FIG. 11, i.e.one group of electrode is used to realize the phase-match for thesub-array which has the same orientation as this group of stripelectrode, and the another group of electrode is used to realize thephase-match for the sub-array which has the same orientation as anothergroup of strip electrode. FIG. 19 illustrates a two-dimensional array ofphase-modulators 12 and the corresponding array of sub-array phasecompensation phase-modulators 42. FIG. 19 contains nine two-dimensionalsub-arrays, and each sub-array has nine phase-modulators. The 17(x1),17(x2) and 17(x3) are the control lines to control the deflection of thebeam of light in x direction. The 17(y1), 17(y2) and 17(y3) are thecontrol lines to control the deflection of the beam of light in ydirection. The array of sub-array phase compensation phase-modulators 42consists of electrode 28 and Electro-optical material between theelectrodes. The l6(x1), 16(x2) and 16(x3) are the control lines for thesub-array phase compensation phase-modulators corresponding to thecontrol signals for deflecting the beam of light in x direction. The16(y1), 16(y2) and 16(y3) are the control lines for the sub-array phasecompensation phase-modulators corresponding to the control signals fordeflecting the beam of light in y direction. The structure shown in FIG.19 coupling with an array of lenses of eighty-one lenses can form aphased-array of eighty-one phase-controlled elements. These eighty-onelenses also form nine sub-arrays accordingly, and each sub-array hasnine lenses. It is pointed out here that the number of sub-arrays andthe number phase-controlled elements do not have to be equal. It canhave other combinations according to the total number ofphase-controlled elements in the phased-array.

The method of the sub-array phase compensation phase-modulator shown inFIG. 18 can also be used for one-dimensional phased-array as shown inFIG. 5, FIG. 6 and FIG. 7. The FIG. 20 illustrates a one-dimensionalarray of phase-modulators 12 with an array of sub-array phasecompensation phase-modulators 43. The FIG. 20 contains threeone-dimensional sub-arrays, and each sub-array has threephase-controlled elements. When using the method of the sub-array phasecompensation phase-modulator as shown in FIG. 20, there is no need toindependently control the common electrode of each sub-array, therefore,the entire array of phase-modulators needs only one common electrode 16.The method of the sub-array phase compensation phase-modulator as shownin FIG. 20 can also be used for two-dimensional phased-array as shown inFIG. 10. A two-dimensional phased-array formed with sub-arrays can beconstructed with two one-dimensional arrays of phase-modulators alongwith the sub-array phase compensation phase-modulator as shown in FIG.20, according to method shown in FIG. 10. At this time, eachtwo-dimensional sub-array actually contains two sub-array phasecompensation phase-modulators. A two-dimensional phased-array withsub-arrays can be constructed with cascading of a two-dimensional arrayof phase-modulators as shown in FIG. 10 along with an arrays ofsub-array phase compensation phase-modulators 42 as shown in FIG. 19.

FIG. 20 uses longitudinal phase-modulator for illustration. Similarly,we can also use the transverse phase-modulators as shown in FIG. 7 toconstruct the array of phase-modulators 12 and array of sub-array phasecompensation phase-modulators 42. When the array of phase-modulators isa transverse phase-modulators as shown in FIG. 7, the array of sub-arrayphase compensation phase-modulators can assume same structure as thearray of phase-modulators, except connecting a number ofphase-modulators in parallel according the size of the sub-array, asshown in FIG. 21. Connecting three phase-modulators in parallel can beused for a sub-array with three phase-modulators.

Regardless of controlling common electrode or sub-array phasecompensation phase-modulator, the control signal is substantially same.It is also one of the advantages of the present invention.

It should be pointed out that for the two-dimensional array of sub-arrayphase compensation phase-modulators shown in FIG. 19 or for thetwo-dimensional array of sub-array phase compensation phase-modulatorsformed by cross-cascading two one-dimensional arrays of sub-array phasecompensation phase-modulators shown in FIG. 20, the independent controlof each sub-arrays is still not an absolutely independent (details willbe in the following). The advantage of doing so is that the controllines are greatly reduced. Such method of sub-array phase compensationphase-modulator array can be used for two-dimensional regularphased-array, can also be used for two-dimensional phased-array withregular placement of irregular sub-arrays (i.e. the phase-controlledelements in each sub-array form an irregular pattern, while thesub-arrays are placed in a regular pattern in the phased-array), detailsare in the following.

The above description is based on the strip phase-modulator array asshown in FIG. 10 and FIG. 11. However, the controlling method can alsobe used for the two-dimensional irregular sub-array based on thephase-modulator array as shown in FIG. 12, FIG. 13 and FIG. 14.

6. The Structure of Sub-array of the Irregular Phased-array

The sub-array technique of the irregular phased-array of presentinvention contains two meanings: First, the sub-array of the irregularphased-array itself is an irregular array. Second, the sub-arrays of theirregular phased-array are placed irregularly with respect to othersub-arrays within the phased-array. We emphases again here that in thesub-arrays of the irregular phased-array, the pattern of the placementof the effective position of the phase-controlled element are identical,though the geometric position, shape and size of the phase-controlledelement may be different with each other.

For the convenience of the description, we define the distance betweenthe effective positions of two phase-controlled elements at the two sideof the boundary between two sub-arrays as “effective spacing” betweenthe sub-arrays. This is the distance between two focal points of thelenses at the two side of the boundary between two sub-arrays. In theFIG. 22 and FIG. 23, e1, e2 and e3 represent the effective spacing. Thedistance between the physical boundary of the two adjacent sub-arrays isdefined as “spacing” between the sub-arrays. In the FIG. 22 and FIG. 23,s1, s2 and s3 represent the spacing. The effective spacing betweensub-arrays in present invention is irregular. That is: not only theeffective position of the phase-controlled elements within sub-arrayforms irregular pattern, but the effective array (i.e. the array of theeffective position of the phase-controlled elements in a sub-array) ofthe sub-array is also placed irregularly with respect to each other inthe phased-array. The method of placing the effective array of thesub-array irregularly in the phased-array is shown in FIG. 22 and FIG.23.

In FIG. 22, in each sub-array, the position of the optical axis 28 (ofthe lens) of the corresponding phase-controlled element relative to theaxis of the geometric center 29 (FIG. 8) of the phase-controlled elementis fixed, i.e. i=j=k. The irregularity of the effective spacing betweensub-arrays is realized through the changing of the spacing betweensub-arrays, i.e. s1≠s2≠s3. In FIG. 23, the spacing between the sub-arrayis kept constant, i.e. s1=s2=s3. The irregularity of the effectivespacing between sub-arrays is realized through changing the position ofthe optical axis 28 of the lens, i.e. in each sub-array, the position ofthe virtual array of the effective point-source of point generated bythe lenses relative to the array of phase-modulators is not fixed,i≠j≠k.

Employing the sub-array technique can significantly reduce the controllines. For example, a phased-array of 1024 phased-controlled elementscan be divided into 32 sub-arrays, and each sub-array contains 32phase-controlled elements. We can use 32 control lines to parallelcontrol the 32 control electrodes of the phase-modulator in eachsub-array, and use another 32 control lines to control the 32 commonelectrodes of the sub-arrays. When using the sub-array phasecompensation phase-modulator, the situation is the same: 32 controllines are used to parallel control the 32 phase-modulators in eachsub-array, and the another 32 control lines are used to control the 32sub-array phase compensation phase-modulators. The total control line is32+32=64. If not using the sub-array technique of the present invention,the 1024 phase-modulators will need 1024 control lines.

In the following, we will further describe the placement of thetwo-dimensional irregularly placed irregular sub-arrays. FIG. 24illustrates an example of a two-dimensional irregularly placed irregularsub-arrays. The figure contains nine two-dimensional irregularsub-arrays, and each sub-array contains nine phase-controlled elements.This two-dimensional array can be constructed with the method shown inFIG. 11 or FIG. 10. The 17(x1), 17(x2) and 17(x3) are the control linesto control the deflection of the beam in X direction. The 17(y1), 17(y2)and 17(y3) are the control lines to control the deflection of the beamin Y direction. Grouping the strip electrode (or the phase-modulatorwith strip electrode) 41 into three groups (one-dimensional array) 30X₁,30X₂ and 30X₃ and another three groups (one-dimensional array) 30Y₁,30Y₂ and 30Y₃. In the figure, the nine dark dot at the crosses of thethree horizontal and three vertical broken lines represent the effectivepositions of the nine phase-controlled elements of each sub-array in thetwo-dimensional phased-array. The 40 _(1,1), 40 _(1,2), 40 _(2,1 9). . .represent each two-dimensional sub-array. Just as illustrated in thefigure, the placement of the effective position of the phase-controlledelement in each two-dimensional sub-array is identical (in this example,within each sub-array, the effective position is placed in rows andcolumns while the distance between the rows and columns is irregular),and the placement of each sub-array is irregular within thephased-array.

Now, the “independent” control of the two-dimensional sub-arrays must becompletely independent. We can use the method shown in FIG. 25 to do theindependent control for each sub-array. The sub-array phase compensationphase-modulator array 42 shown in FIG. 25 is formed by thephase-modulator that consists of control electrode 44, common electrode39 and the Electro-optical material between the two electrodes. The sizeof each sub-array phase compensation phase-modulator is as large as thecorresponding sub-array. The sub-array phase compensationphase-modulator array 42 in FIG. 19 can be replaced with the sub-arrayphase compensation phase-modulator array 45 in FIG. 25. The sub-arrayphase compensation phase-modulator array 45 in FIG. 25 can also becascaded with two one-dimensional (strip electrode) phase-modulatorarrays. It is also possible that in the structure shown in FIG. 10,changing the common electrode of a one-dimensional (strip)phase-modulator array into the electrode that is just like the controlelectrode 44 of the sub-array phase compensation phase-modulator array45 in FIG. 25, such that each two-dimensional sub-array has a completeindependent common electrode. For a two-dimensional irregularphased-array of 1000×1000 (i.e. a million) phase-controlled elements, itcan be divided into 100 sub-arrays, and each sub-array contains 100×100(i.e. 10,000) phase-controlled elements. Thus, we can use 100 controllines to parallel control the strip control electrode of each sub-arrayto steer the beam of light in X direction, and use 100 control lines toparallel control the strip control electrode of each sub-array to steerthe beam of light in Y direction, and use another 100 control lines tocontrol the sub-array phase compensation phase-modulator (or commonelectrode) of each sub-array to achieve phase match among the light fromeach sub-array. The total control lines are 300. If not using thesub-array technique of the present invention, it will need two thousandcontrol lines. If not using the strip electrode structure, it will needa million control lines.

7. Reflective Irregular Phased-array

In the description of the above, we use the transmission irregularphased-array as example. However, the principle, concept and methodproposed in the present invention can also be used for reflectiveirregular phased-array. Here, we only describe some special features ofa reflective irregular phased-array, and the content similar to what hasbee mentioned above will not be repeated.

FIG. 26 illustrates one way in which a reflective irregular phased-arrayis operated. The beam of light 18, from the light source 33, verticallyincidents in, and passes the phase-modulator array 12, and then isreflected back by the array of minors 32 that is coupled with thephase-modulator array 12. The reflected light passes the phase-modulatorarray 12 again, and is focused by the minors 32. At the focal points ofthe minors, the irregular virtual array of effective point-source oflight is created. By adjusting the phase of the light from each element,we can steer the beam of light to a given direction (e.g. to the screen34). Here, similar to the transmission irregular phased-array, theeffective position of each phase-controlled element is defined by thefocal point of the minor, and the effective position of eachphase-controlled element is generally not coincident with the geometriccenter of the phase-controlled element. Similar to the case of lens,generally, the mirror is not symmetrical. FIG. 27 further illustratesthe structure of the reflective irregular phased-array. Incident light18 pass through the phase-modulator array 12, is reflected back by theminors, and is focused at the focal point 36. Therefore, the irregularvirtual phased-array of effective point source of light is created atthe focal point 36.

Since the light passes the phase-modulator twice, therefore, under samecondition, the thickness of the phase-modulator needed is only half ofthat for transmission phased-array, or, the voltage of the controlsignal needed is only half of that for a transmission phased-array.

Since the source of the light is in front of the irregular phased-array,to avoiding the beam of light from the phased-array from being blocked,we can shift the canning range to one side, e.g. shift upwards, as shownin FIG. 26. In this situation, we can tilt the mirrors to increase theefficiency of the reflective irregular phased-array. It should bepointed out that strictly speaking, at this time, 36 in FIG. 28 is theconvergent point of the light, is not necessary the focal point of themirror. But for the simplicity of description, we neglect thedifference. In FIG. 28, the optical axis 35 of the mirror has an anglewith respect to the normal direction 49 of the phased-array in order theto make the divergent range of the light from each element matches thescanning angular range of the phased-array. That is to say: in general,the optical axis of the mirror does not coincident with the axis of thegeometric center of the corresponding phase-modulator, nor is parallelto the axis geometric center of the corresponding phase-modulator.

The minor dose not have to be the concave mirror as shown in FIG. 27 orFIG. 28. It can also be a combination of plan mirror, lens and grating.There is no substantial difference in principle and structure from theconcave mirror as being used in present invention. Similar to the methodof the lens, by choosing the optical parameters of the mirror such asaperture, focal length etc., the divergent angle of the light from eachphase-controlled element can be controlled.

The various methods about the array of phase-modulators mentioned abovecan also be used for the reflective irregular phased-array, includingone-dimensional array and various two-dimensional arrays. The sub-arraymethods mentioned before can also be used for the reflective irregularphased-array, therefore, we do not repeat these here.

8. Phase-controlled Light Emitter Array

As mentioned before, the prior art requires the distance betweenphase-controlled elements to be less than half wavelength (or onewavelength). Using 0.5 μm wavelength visible light as an example, itwill require the distance between the phase-controlled elements to beless than 0.25 μm, therefore, the size of the phase-controlled elementsmust also be less than 0.25 μm. It is impossible to fabricate an arrayof phase-controlled light emitter with present technology in suchcompact space. However, the principle, concept and method of theirregular phased-array of the present invention can be used to constructa phase-controlled light emitter array, besides the space-fedphased-array described above. The present invention makes the distancebetween the phase-controlled elements no longer be limited by thewavelength of the light, therefore, the distance can be tens, thousandstimes of the wavelength, or even larger, thus, there will be enoughspace between the phase-controlled light emitters to be used toconstruct the electric circuit and structure to control the phase of thelight from the light emitter. That makes the constructingphase-controlled light emitter array possible.

The phase-controlled light emitter means the light emitter that thephase of the light produced can be controlled, including various typesof laser, light amplifier, optical fiber laser and laser diode etc.Large aperture phased-array can be fabricated with discretephase-controlled light emitter, and phase-control unit. For smallaperture phased-array, the light emitter and the control structure andcircuit for the light emitter can be integrated together withmicro-electronic technique.

FIG. 29, FIG. 30 and FIG. 31 illustrate the irregular phased-array basedon phase-controlled light emitter. FIG. 29 illustrates the irregularphased-array constructed with small size light emitter 37. The irregulararray is formed with the irregular placement of the light emitteritself. When the size the light emitter is comparable to the wavelength,the light will divergent significantly, therefore no lens is needed.Since the light emitter itself can control the phase of the light, noextra electro-optical phase-modulator, as described before, is needed.

When the size the light emitter is large, lens 23 is needed to divergethe light as shown in FIG. 30. The method of virtual array of effectivepoint source of light mentioned above can be used to create theirregular phased-array. For the same reason as mentioned above, theelectro-optical phase-modulator is not needed. If the light emitter dosenot have enough phase control capability, for example, if the light fromthe light emitter can only maintain a fixed phase relationship with eachother, or even a fixed phase relationship can not be maintained, thenthe phase-modulator 12 as described before will be needed, as shown inFIG. 31. When the light emitter can not maintain a fixed phaserelationship with each other for a long period of time, it is stillpossible to use the method shown in FIG. 31 , as long as the phase ofthe light from the emitter is stable enough for a certain period oftime. In this case, we can measure the change of the phase relationshipamong the light from the light emitter after every short period, candynamically compensate the drafting of the phase.

The various methods describe above, including the placement of thephase-controlled element, virtual effective point source of light andsub-array can also be used for the irregular phased-array constructedwith phase-controlled light emitter. Since this is obvious, we do notrepeat the description here.

In the above, we have described the method, feature and advantage of thepresent invention with assistant of the figures. However, the presentinvention is not limited to the particular embodiments mentioned above.For the people with the skill of the art, to make some variations andmodifications within the principle and method of present invention isobvious. The claims of the present invention cover all the variations,modifications and equivalent devices based on the present invention.

What is claimed is:
 1. An optical irregular phased-array device,comprising of an array of phase-controlled elements, a controller andcontrol lines connecting the said controller and the said array ofphase-controlled elements, the effective positions of the saidphase-controlled elements are randomly arranged to form a knownirregular pattern, wherein the average distance between the effectivepositions of adjacent phase-controlled elements is substantially greaterthan the wavelength of the light to be steered by the said phased-array.2. The device according to claim 1, wherein the said array ofphase-controlled elements comprises an array of electro-opticalphase-modulators.
 3. The device according to claim 2, wherein the saidphased-controlled element further includes a lens or a mirror at leastone of them, and the focal points or the virtual focal points of thesaid lenses or mirrors of the plurality of the said phase-controlledelements form an irregular array.
 4. The device according to claim 3,wherein the said lens is a diverging lens or a converging lens, at leastone of them.
 5. The device according to claim 4, wherein the said lensis an asymmetrical lens.
 6. The device according to claim 3, wherein thesaid mirror is a concave mirror or a plan mirror.
 7. The deviceaccording to claim 6, wherein the said concave mirror is an asymmetricalmirror.
 8. The device according to claim 6, wherein the optical axis ofthe said mirror is tilted relative to the normal direction of thephase-array.
 9. The device according to claim 1, wherein the saidphase-controlled elements form a regular array.
 10. The device accordingto claim 1, wherein the said irregular phased-array is a two-dimensionalirregular phased-array.
 11. The device according to claim 10, whereinthe said irregular pattern of the said effective positions of the saidphase-controlled elements is a pattern wherein the said effectivepositions of the said phase-controlled elements are aligned in rows andcolumns with irregular distances between the rows and columns.
 12. Thedevice according to claim 2, wherein the said irregular phased-arraycomprises plurality of sub-arrays, the said sub-array comprisesplurality of the said phase-controlled elements, the effective positionsof the said phase-controlled elements in the said sub-array are randomlyarranged to form a known irregular array, and the said irregular arraysof the effective positions of the said phase-controlled elements of thesaid sub-arrays are placed irregularly with respect to each other in thephased-array that is formed by the sub-arrays.
 13. The device accordingto claim 12, wherein the said irregular phased-array comprises means forparallel controlling of the sub-arrays and independent controlling ofeach sub-array.
 14. The device according to claim 13, wherein the saidmeans of independent controlling of each sub-array including independentcommon electrode for the phase-modulators of the phase-controlledelements of each sub-array, and means to independently control thecommon electrode of each sub-array.
 15. The device according to claim13, wherein the said means of independent controlling of each sub-arrayincluding an additional sub-array phase-compensation phase-modulator foreach sub-array, and means of independently control the sub-arrayphase-compensation phase-modulator of each sub-array.
 16. The deviceaccording to claim 12, wherein the said irregular phased-array is atwo-dimensional irregular phased-array.
 17. The device according toclaim 16, wherein the said irregular array of the said effectivepositions of the said phase-controlled elements of each sub-array is asuch pattern that the said effective positions of the saidphase-controlled elements are aligned in rows and columns with irregulardistances between rows and columns.
 18. The device according to claim17, wherein the said array of electro-optical phase-modulators includinga two-dimensional phase-modulators that are formed with two crosscascaded one-dimensional arrays phase-modulators.
 19. The deviceaccording to claim 18, wherein the said one-dimensional array ofphase-modulators including longitudinal phase-modulators or transversephase-modulators, at least one of the two.
 20. The device according toclaim 1, wherein the average distance between the effective positions ofadjacent phase-controlled elements is more than ten times of thewavelength of the light which the phase-array is concerned for.
 21. Thedevice according to claim 1, wherein the said phase-controlled elementsare placed in a regular pattern with the center-to-center distancebetween adjacent phase-controlled elements equal to the average distancebetween the effective positions of adjacent phase-controlled elements,and the effective position of a phase-controlled element is randomlylocated with equal probability around the geometric center of thephase-controlled element.
 22. The device according to claim 2, whereinthe said array of electro-optical phase-modulators including atwo-dimensional array of electro-optical phase-modulators formed withtwo groups of strip-electrodes, which are cross to each other, at thetwo sides of an electro-optical material respectively.
 23. An opticalphased-array device, comprising means of generating an array of virtualeffective point-source of light, and means of modulating the phase ofthe light for each said virtual effective point-source of light.
 24. Thedevice according to claim 23, wherein the said means of generating anarray of virtual effective point-source of light including an array oflenses or an array of mirrors, at least one of them.
 25. The deviceaccording to claim 24, wherein the said array of virtual effectivepoint-source of light is an irregular array, and the average distancebetween the adjacent effective point-source of lights is greater thanten times of the wavelength of the light which the said phased-array isconcerned for; the said means of modulating the phase of the light foreach said virtual effective point-source of light includingelectro-optical phase-modulator.
 26. The device according to claim 25,wherein the said lenses or mirrors form a regular array while theirfocal points form an irregular array; the said lenses or mirrors are ingeneral asymmetrical.
 27. The device according to claim 26, wherein thesaid irregular array of virtual effective point-source of light is atwo-dimensional irregular array.
 28. The device according to claim 27,wherein the said virtual effective point-source of light are aligned inrows and columns with irregular distances between the rows and columns.29. The device according to claim 28, wherein the said irregular arrayof virtual effective point-source of light comprises of plurality ofidentical irregular sub-arrays, each sub-array comprises plurality ofvirtual effective point-source of light, the placement of the saidirregular sub-arrays is also irregular with respect to each other in thesaid irregular array of virtual effective point-source of light.
 30. Thedevice according to claim 29, wherein the said means of modulating thephase of the light for each said virtual effective point-source of lightincluding the means of modulating the sub-arrays in parallel and themeans of modulating each sub-array independently.
 31. The deviceaccording to claim 30, wherein the said means of modulating eachsub-array independently including a common electrode for the saidelectro-optical phase-modulators in each sub-array independent of othersub-arrays, and an additional sub-array phase-compensationphase-modulator for each sub-array, at least, one of the two means. 32.The device according to claim 31, wherein the said phase-modulators ineach sub-array form a regular array.
 33. An optical irregularphased-array device, comprising plurality of substantially identicalirregular sub-arrays, each said irregular sub-array comprises pluralityof phase-controlled elements whose effective positions form an irregulararray within each sub-array, the average distance between the effectivepositions of adjacent phase-controlled elements is substantially greaterthan the wavelength of the light which the said phased-array isconcerned for, the said irregular arrays of the effective positions ofthe phase-controlled elements of said sub-arrays are placed irregularlywith respect to each other in the said irregular phased-array; the saidirregular phased-array further comprises means of defining the saideffective position of each phase-controlled element; the said irregularphased-array further comprises means for control of the sub-arrays inparallel and means for control of each sub-array independently.
 34. Thedevice according to claim 33, wherein the said phase-controlled elementcomprises electro-optical phase-modulator, the said means for control ofthe sub-arrays in parallel comprises the parallel linkage of thecontrol-electrodes of the said phase-modulators at the correspondingpositions in each sub-array; the said means for control of eachsub-array independently comprises an independent common electrode forthe said phase-modulators of each sub-array independently with respectto the common electrodes of the phase-modulators of other sub-arrays,and an additional sub-array phase-compensation phase-modulator for eachsub-array, which can be controlled independently with respect to theadditional sub-array phase-compensation phase-modulators of othersub-arrays, at least one of the two means.
 35. The device according toclaim 34, wherein the said means of defining the said effective positionof each phase-controlled element comprises a lens or a mirror for eachphase-controlled element at least one of them.
 36. The device accordingto claim 35, wherein the said irregular placement of the said irregulararrays of the effective positions of the phase-controlled elements ofsaid sub-arrays comprises means of placing the arrays of saidelectro-optical phase-modulators of each sub-arrays regularly withrespect to each other.
 37. The device according to claim 36, wherein thesaid lens or mirror including asymmetrical lens or mirror.
 38. Thedevice according to claim 37, wherein the said irregular phased-array isa two-dimensional phased-array that comprises plurality oftwo-dimensional irregular sub-arrays.
 39. The device according to claim38, wherein the said effective positions of the phase-controlledelements in each sub-array are aligned in rows and column with irregulardistances between the rows and columns.
 40. The device according toclaim 35, wherein the said lens or mirror including cylindrical lens orcylindrical mirror.